NO. 1846. ON CERTAIN ELEUTHEROZOW PELMATOZOA—KIRK. 41 



rapidly than the arms. If actually assisting in the locomotion of 

 the animal it is evident, as suggested above, that the cirri functioned 

 merely in raising the animal from the bottom. Lateral motion 

 could only be effected through the action of the arms, which, on the 

 other hand, would have slight value in bringing about vertical 

 movement. 



Effect of detachment on Jiahits of the Pentacrinidse. — The life history 

 of the Pentacrinidse as bearing on their colonial habit may be dealt 

 with to better advantage in a subsequent paper where the facts 

 relating to the segregation of the Crinoidea are treated in detail. A 

 description of the conditions under which Isocrinus has been dredged, 

 as given by Agassiz (1888, vol. 2, p. 117), may well be quoted at tliis 

 time, however, as perhaps indicating the general habits of the detached 

 forms. "A similar entangling also occurred among the specimens 

 dredged by the Blake, and it was often very difficult to separate 

 specimens, the cirri of which had become attached to adjoining stems. 

 It is possible that they live gregariously, more or less united either 

 by the twisting of the stem or the grappling of the cirri, and be only 

 loosely attached to the ooze in which they live, or anchored more 

 firmly by the terminal whorl to some projecting piece of rock or 

 gorgonia stem." Doderlein (1907, p. 30) has described similar 

 colonies in the case of adult Metacrinus. In this genus a considerable 

 length of the distal portion of the column lies horizontally upon the 

 bottom and is inextricably entangled with the columns of other 

 individuals, corals, and other lime-secreting organisms. His descrip- 

 tion of such a colony is here given in part : 



Da, wie es scheint, diese Crinoiden gewohnlich in grosseren Mengen beisammen 

 etehen, formliclie " Wiilder" bildend, so ist anzunehmen, dass die horizoutalen Teile 

 ihrer Stiele uber und nebeii einander auf dem Boden liegend, mit iliren unzahligen 

 Ranken in einander verkrallt,ein unentwirr bares, iunig zusammenhangendes Geflecht 

 bUden , das als eine miichtige, fast unzerreissbare Masse den Untergrund eines Crinoiden- 

 waldes bildet. aus dem sich dann die einzelnen Kelche auf mehr oder weniger langen, 

 garaden Stielen frei erheben. 



In the case of both Isocrinus and Metacrinus I hold that this 

 mutual entangling of the organisms follows a period of complete 

 detachment durmg which a certain degree of movement is possible. 

 During this period of freedom selective migration of a more or less 

 effective sort may take place. 



In this connection may be mentioned a curious belief of the Japa- 

 nese fishermen relative to the location of Metacrinus rotundus. As 

 is well known a large number of the specmaens of Metacrinus rotundus 

 have been obtained by the Japanese fishermen, who, upon hauling 

 m their enormous trawls, occasionally find a Metacrinus entangled in 

 the hooks. In this way, also, are obtamed many of the exceedingly 

 rare sponges and other organisms of this region. I have been 



